The present invention relates to the field of transport. It relates to a transporting apparatus according to the preamble of claim 1 and to a method of operating such a transporting apparatus.
A transporting apparatus of the type mentioned is known, for example, from U.S. Pat. No. 4,896,610.
Transporting apparatuses in which a transporting platform can be moved in a largely friction-free manner by means of an air cushion generated between the transporting platform and a transporting plane have been known for some time now. It is possible here for the air cushion to be generated either by the platform itself or by an apparatus arranged beneath the transporting plane. A known example of the first-mentioned alternative is constituted by the sea-going and land-bound vehicles for passenger transport which have become known as hovercrafts.
The second-mentioned alternative is used, in particular, wherever, on the one hand, there are transporting planes with a comparatively small lateral extent present and, on the other hand, the transporting platform itself is intended to be constructed as straightforwardly as possible and without any additional installations and energy sources. U.S. Pat. No. 3,610,695 thus describes a (horizontally operating) transporting apparatus for metal plates, in the case of which the metal plate which is to be transported is mounted, and moved in a friction-free manner, on an air cushion. The air cushion is generated by air which flows out continuously into the interspace between the metal plate and transporting surface through nozzles distributed uniformly in the transporting surface. The metal plate is moved by an electromagnetically acting linear motor which is formed by coils arranged in iron cores beneath the transporting surface. The coils are activated in accordance with the current position of the metal plate, this position being determined by (optical) sensors located above the metal plate. The disadvantage with this solution is that air flows out uniformly through all the air nozzles of the transporting apparatus irrespective of where the metal plate is actually located. The disruptive arrangement of the sensors above the metal plate which is to be transported is also disadvantageous. Finally, the linear motor has the disadvantage that it is not only associated with considerable outlay, as far as its construction and operation are concerned, but is also inflexible in terms of transporting direction, because it only allows one movement direction.
A further transporting apparatus with a combination of linear motor and mounting on an air cushion is described in U.S. Pat. No. 4,077,507.
U.S. Pat. No. 3,648,852 discloses a transporting apparatus with two parallel sliding rails on which a transporting pallet can be displaced horizontally. Air channels for generating an air cushion open out in a uniformly distributed manner into the planar top surfaces of the sliding rails. The air channels are closed in each case by a ball valve, of which the ball, in the closed state of the valve, projects a little beyond the top surface of the sliding rails. The ball valves are only opened when the transporting pallet, as it slides over the valves, presses the associated balls, counter to the pressure of a spring, into the top surface of the sliding rails. This achieves the situation where only those ball valves and/or air channels which are actually required beneath the transporting pallet for forming the air cushion are activated. The disadvantage here, however, is the mechanical engagement between the transporting pallet and the valve balls, which obstructs the movement, results in wear and renders the functioning of the arrangement susceptible to disruption. It is also the case here that the movement direction is limited by the direction of the sliding rails. Furthermore, an active movement mechanism is not provided in the case of this transporting apparatus.
U.S. Pat. No. 4,896,610, mentioned in the introduction, proposes a transporting apparatus which acts in two independent directions and in the case of which air nozzles provided with valves are distributed uniformly on the transporting surface. In a manner similar to U.S. Pat. No. 3,648,852, the valves may be designed as ball valves, which are actuated mechanically by the transporting platform. However, it is also proposed (page 2, lines 34-63 of the document) to use electrically switched valves which are opened by different proximity detection systems when the platform approaches the valves. In addition to the transporting platform being mounted on a planar air cushion, a description is also given of possible ways in which the platform can be actively advanced by means of an advancement mechanism. One possibility consists in using a hydraulically actuated repulsion mechanism (FIG. 10) fitted on the platform. Another possibility for an advancement mechanism consists in using two magnetic plates on the platform which are each made to rotate by a battery-operated motor and interact with the metallic transporting surface (FIG. 11). The disadvantage here is that, on account of the advancement mechanism installed, the transporting platform has a comparatively complicated construction and requires a dedicated energy source. The fact that a wire-bound or wireless connection to the platform has to be provided in order to control the movement is also disadvantageous.
It is thus an object of the invention to provide a transporting apparatus, with air supply through the transporting plane, which avoids the disadvantages of the known transporting apparatuses, is distinguished, in particular, by simplified and functionally reliable control and can be used to realize an active movement mechanism without high outlay. It is also an object of the invention to specify a method of operating such a transporting apparatus.
The objects are achieved by the features of claims 1 and 10 taken as a whole. The core of the invention consists in designing the valves of the air nozzles as solenoid valves equipped with a magnet coil and in providing the transporting platform with ferromagnetic regions which interact with the magnet coils of the solenoid valves in dependence on the position of the transporting platform. It is thus easily possible, with a (passive) transporting platform, for the various tasks of valve control, localization and active advancement of the transporting platform to be achieved reliably via a single mechanism.
It is conceivable, in principle, for the transporting platform only to be provided with ferromagnetic regions on the periphery. By the interaction with the solenoid valves, this then establishes, in the transporting plane, the edge of an area which corresponds to the extent of the transporting platform. A control means can then determine which solenoid valves are located inside, and which are located outside, this area and can actuate one or more solenoid valves located within the area. The transporting apparatus is particularly straightforward if, according to a preferred configuration, the transporting platform is designed as a ferromagnetic carrier plate (throughout). This easily achieves interaction with all the solenoid valves located beneath the platform and/or the carrier plate.
The interaction is particularly intensive if the magnet coils of the solenoid valves are designed as ring coils and are arranged beneath the transporting plane with the coil axis perpendicular to the transporting plane, if a non-magnetic cover plate, preferably made of aluminum, is arranged between the magnet coils and the transporting plane, and the air nozzles are formed by bores in the cover plate, and if the magnet coils are arranged in each case in a yoke which is made of ferromagnetic material and is open in the direction of the transporting plane.
If the magnet coils are intended to be used, at the same time, for the active advancement of the transporting pallet, it is advantageous for the solenoid valves to be designed such that they are closed in the de-energized state of the magnet coil and open when the magnet coil is supplied with a current of suitable magnitude, it being the case that, in the de-energized state of the magnet coil, the solenoid valves are kept closed in each case by a spring element.
A maximum level of flexibility can be achieved in the case of the transporting apparatus in that the solenoid valves are connected to a control means such that they can be activated individually. It is expedient, in particular, if the solenoid valves are arranged in a two-dimensional matrix in the transporting plane and are connected to the control means via corresponding control lines which are assigned to the rows and columns of the matrix.
A preferred configuration of the method according to the invention is characterized in that the extent and/or the position of the transporting platform are/is determined from the measured inductances of the magnet coils. It is thus possible for different transporting platforms to be moved at the same time on the transporting apparatus. Active advancement of the transporting pallet can be achieved easily and without additional auxiliary means, according to one configuration of the invention, in that, utilizing the interaction between the transporting platform and the magnet coils of the solenoid valves, the transporting platform is moved in a predetermined movement direction by selected solenoid valves being switched on and off.
Further embodiments can be gathered from the dependent claims.